A relative afferent pupillary defect (RAPD), also known as a Marcus Gunn pupil, is a medical sign observed during the swinging-flashlight test[1] whereupon the patient's pupilsdilate when a bright light is swung from the unaffected eye to the affected eye. The affected eye still senses the light and produces pupillary sphincter constriction to some degree, albeit reduced.
Relative afferent pupillary defect
Other names
Marcus Gunn pupil
The left optic nerve and the optic tracts. A Marcus Gunn pupil indicates an afferent defect, usually at the level of the retina or optic nerve. Moving a bright light from the unaffected eye to the affected eye would cause both eyes to dilate, because the ability to perceive the bright light is diminished.
The Marcus Gunn pupil is a relative afferent pupillary defect indicating a decreased pupillary response to light in the affected eye.[3]
In the swinging flashlight test, a light is alternately shone into the left and right eyes. A normal response would be equal constriction of both pupils, regardless of which eye the light is directed at. This indicates an intact direct and consensual pupillary light reflex. When the test is performed in an eye with an afferent pupillary defect, light directed in the affected eye will cause only mild constriction of both pupils (due to decreased response to light from the afferent defect), while light in the unaffected eye will cause a normal constriction of both pupils (due to an intact efferent path, and an intact consensual pupillary reflex). Thus, light shone in the affected eye will produce less pupillary constriction than light shone in the unaffected eye.[citation needed]
Anisocoria is absent. A Marcus Gunn pupil is seen, among other conditions, in unilateral optic neuritis.[4] It is also common in retrobulbar optic neuritis due to multiple sclerosis but unreliable in bilateral optic neuritis.[4][5]
A total CN II lesion, in which the affected eye perceives no light, is very similar to a Marcus Gunn pupil; to distinguish them, in a CNII total lesion shining the light in the affected eye produces zero dilation nor constriction.
relative, afferent, pupillary, defect, winking, syndrome, marcus, gunn, phenomenon, relative, afferent, pupillary, defect, rapd, also, known, marcus, gunn, pupil, medical, sign, observed, during, swinging, flashlight, test, whereupon, patient, pupils, dilate, . For the jaw winking syndrome see Marcus Gunn phenomenon A relative afferent pupillary defect RAPD also known as a Marcus Gunn pupil is a medical sign observed during the swinging flashlight test 1 whereupon the patient s pupils dilate when a bright light is swung from the unaffected eye to the affected eye The affected eye still senses the light and produces pupillary sphincter constriction to some degree albeit reduced Relative afferent pupillary defectOther namesMarcus Gunn pupilThe left optic nerve and the optic tracts A Marcus Gunn pupil indicates an afferent defect usually at the level of the retina or optic nerve Moving a bright light from the unaffected eye to the affected eye would cause both eyes to dilate because the ability to perceive the bright light is diminished SpecialtyOphthalmology OptometryDepending on severity different symptoms may appear during the swinging flash light test Mild RAPD initially presents as a weak pupil constriction after which dilation occurs When RAPD is moderate pupil size initially remains same after which it dilates When RAPD is severe the pupil dilates quickly Contents 1 Cause 2 Diagnosis 3 See also 4 References 5 External linksCause editThe most common cause of Marcus Gunn pupil is a lesion of the optic nerve between the retina and the optic chiasm due to glaucoma asevere retinal disease or due to multiple sclerosis It is named after Scottish ophthalmologist Robert Marcus Gunn 2 A second common cause of Marcus Gunn pupil is a contralateral optic tract lesion due to the different contributions of the intact nasal and temporal hemifields 3 Diagnosis editThe Marcus Gunn pupil is a relative afferent pupillary defect indicating a decreased pupillary response to light in the affected eye 3 In the swinging flashlight test a light is alternately shone into the left and right eyes A normal response would be equal constriction of both pupils regardless of which eye the light is directed at This indicates an intact direct and consensual pupillary light reflex When the test is performed in an eye with an afferent pupillary defect light directed in the affected eye will cause only mild constriction of both pupils due to decreased response to light from the afferent defect while light in the unaffected eye will cause a normal constriction of both pupils due to an intact efferent path and an intact consensual pupillary reflex Thus light shone in the affected eye will produce less pupillary constriction than light shone in the unaffected eye citation needed Anisocoria is absent A Marcus Gunn pupil is seen among other conditions in unilateral optic neuritis 4 It is also common in retrobulbar optic neuritis due to multiple sclerosis but unreliable in bilateral optic neuritis 4 5 A total CN II lesion in which the affected eye perceives no light is very similar to a Marcus Gunn pupil to distinguish them in a CNII total lesion shining the light in the affected eye produces zero dilation nor constriction See also editArgyll Robertson pupil Adie syndrome Cycloplegia Miosis Parinaud s syndrome SyphilisReferences edit Pupillary Responses Stanford University School of Medicine Retrieved 2015 11 04 doctor 2687 at Who Named It a b Pearce J November 1996 The Marcus Gunn pupil J Neurol Neurosurg Psychiatry 61 5 520 doi 10 1136 jnnp 61 5 520 PMC 1074053 PMID 8937350 a b Petzold Axel Fraser Clare L Abegg Mathias Alroughani Raed Alshowaeir Daniah Alvarenga Regina Andris Cecile Asgari Nasrin Barnett Yael Battistella Roberto Behbehani Raed Berger Thomas Bikbov Mukharram M Biotti Damien Biousse Valerie 2022 Diagnosis and classification of optic neuritis PDF The Lancet Neurology 21 12 1120 1134 doi 10 1016 s1474 4422 22 00200 9 ISSN 1474 4422 PMID 36179757 S2CID 252564095 Mumenthaler Neurology 4ed Thieme 2004 page 486 Demyelinating diseasesExternal links edit Retrieved from https en wikipedia org w index php title Relative afferent pupillary defect amp oldid 1191215634, wikipedia, wiki, book, books, library,
